Object cartridge wherein the specimen carrier is surrounded by a cooling chamber



March 12, 1968 H e. HEIDE 3,373,277

OBJECT CARTRIDGE WREREIN THE SPECIMEN CARRIER IS SURROUNDED BY A COOLING CHAMBER Filed Dec. 27, 1965 4 Sheets-Sheet 1 March 12, 1968 3, Hang 3,373,277

OBJECT CARTRIDGE WHEREIN THE SPECIMEN CARRIER IS SURROUNDED BY A COOLING CHAMBER Filed Dec. 27, 1963 4 SheetsSheet 2 I 76' I I I 9 QQJ 8 F 7\ I Kr l i I W g\\ j 1 x Jizzfezfok v i @725 6217fl6) March 12, 1968 H. G. HEIDE 3,373,277

OBJECT CARTRIDGE WHEREIN THE SPECIMEN CARRIER IS SURROUNDED BY A COOLING CHAMBER Filed Dec. 27, 1963 4 Sheets-Sheet 5 man 21 07am lwglfflra e ade March 12, 1968 H. G. HEIDE 3,373,277

OBJECT CARTRIDGE WHEREIN THE SPECIMEN CARRIER IS SURROUNDED BY A COOLING CHAMBER Filed Dec. 27, 1965 4 Sheets-Sheet 4.

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United States Patent 3,373,277 OBJECT CARTRIDGE WHERETN TI-IE SPECIMEN CARRIER 1S SURROUNDED BY A COOLING CHAD/ BER Hans Gunther Heide, Berlin-Charlottenhurg, Germany, assignor to Max-Planck-Gesellschaft zur Forderung der- Wissenschaften e.V.

Filed Dec. 27, 1963, Ser. No. 333,912 Ciaims priority, application Germany, Apr. 19, 1963, M 56,547 29 Claims. (Cl. 250-495) The invention disclosed herein is concerned with corpuscular ray apparatus operating on a pump, especially an electron microscope, provided with an object or specimen cartridge which receives the object or specimen carrier and which is connected with a deep freeze device.

A problem which has been known for a long time in connection with corpuscular ray apparatus operating on the pump, and for which no satisfactory solution has been found until now despite many endeavors undertaken in the art, has to do with the prevention of contamination or soiling of the specimen.

The contamination entails appearance upon the specimen which is to be investigated, of layers caused by polymerization and reduction, under the influence of the corpuscular ray, of hydrocarbon substances which are resent in the residual gases in the vacuum space of the corpuscular ray apparatus. These layers have a disturbing effect, for example, in the case of electron microscopes, in that they reduce the contrast, blurring the contours of the electron optical image and darkening the image, thus rendering the working dificult and frequently making it impossible to utilize the resolution which can be obtained with the apparatus.

It is known that the specimen contamination or, more accurately, the speed at which the contamination takes place, that is, the speed at which the polymerization or hydrocarbon layers grow upon the specimen, depends substantially upon the following four factors:

(1) The contamination speed grows with the partial pressure of the hydrocarbon vapors which contribute to the contamination. The hydrocarbon substances which are thereby concerned come, for example, from sealing grease, pump seals and the lik some low molecular hydrocarbon substances having no part in the contamination.

(2) The contamination speed drops with increasing temperature of the specimen surface. This may be explained by the fact that the dwelling time of the hydrocarbon molecules upon the specimen surface decreases with increasing temperature.

(3) The contamination speed increases with increasing intensity of the irradiation, which is understandable upon considering the fact that the corpuscular ray gives rise to the polymerization and reduction of the hydrocarbon substances upon the specimen.

(4) The contamination speed also depends upon the number and type of other particles (atoms, molecules, ions) impacting the specimen surface,

Known methods and devices for reducing the specimen contamination are directed to the causes noted above in paragraphs (1) and (2), considering thereby the fact that the intensity of the radiation is generally fixedly established by the required radiation conditions, that is, for example, by the desired magnification and image brightness to be obtained with an electron microscope. Only little importance was heretofore attributed to conditions according to the above noted paragraph (4), that is, to the number and type of other particles which impact the specimen.

It was accordingly proposed to heat the specimen so as till to reduce the dwelling time upon the specimen surface, of the molecules which give rise to the contamination, thereby reducing the contamination speed. However, the heating of the specimen for purposes of reducing the specimen contamination is practicaly excluded since a reduction of the contamination speed, to an extent required, for example, for fine-structure investigations, is practically effected only at temperatures in the order of magnitude of 250 C. at which temperatures the specimen is generally destroyed.

There now would remain solely the measure of reducing the partial pressure of the hydrocarbon substances which contributes to the contamination, that is, elimination of the cause for the appearance of contamination, noted above in paragraph (1).

The various objects and features of the invention will appear from the description which is rendered below with reference to the accompanying drawings.

FIG. 1 shows a graph indicating the relation between the contamination speed plotted along the ordinate and the temperature of the cooling chamber or the specimen, respectively, plotted along the abscissa;

FIG. 2 represents the local distribution of the contamination speed V, the specimen break-down A and the curve V-f-A resulting from these two factors;

FIG. 3 indicates the Working range and temperatures at which a specimen contamination or specimen breakdown practically disappears; and

FIGS. 4 to 7 illustrate embodiments of the invention.

Laboratory devices have become known, wherein the specimen which is to be examined is disposed within a cooling trap comprising a system surrounding the specimen and filled with liquid air. The specimen is thereby held by parts which have no connection with the cooling system. However, as intimated above, and as is also mentioned in pertinent publications, this arrangement has been tested only in the laboratory, since the structural realizaiton required for practical application thereof in connection with an electron microscope, encounters considerable ditficulties.

A known device for cooling specimen in electron microscopes comprises a specimen cartridge which is constructed so that the specimen with the specimen carrier are disposed within a cooling chamber having walls which conduct heat well, such chamber being in good heat conducting connection with a cooling agent, for example, liquid air. The specimen as well as the vicinity thereof are thereby cooled to temperatures in the neighborhood of C. This arrangement makes it indeed possible to reduce the contamination speed down to the value zero.

It will be seen from FIG. 1 that contamination grows with increasing temperature'at temperatures above about 30 C., while the contamination speed is reduced to the value zero at temperatures lying, for example, below 30 C. The temperature assigned to the value zero for the contamination speed is subjected to strong dispersion, which is indicated in FIG. 1 by the cross hatched band.

However, at temperatures below the temperature assigned to the contamination speed zero, there is also observed a phenomenon, namely, a specimen break-down, which is, for example, in connection with electron microscopic investigations likewise very disturbing. It will be seen from FIG. 1 that this specimen break-down, which is likewise subjected to strong dispersion, can strongly increase with decreasing temperature.

The ideal solution for the problem of specimen contamination, namely, contamination speed zero and avoidance of any specimen break-down, would accordingly require, in connection with the above indicated known device, accurate adjustment of the specimen temperature,

a a so that the workin point lies, with consideration of the operating conditions of the corpuscular ray apparatus and the special properties of the spechnen which is to be investigated, exactly upon the abscissa axis.

It must be considered in this connection, with reference to FIG. 2, showing the local distribution of the contamination speed V, the specimen breakdown A and the resulting curve V+A, that there is no constant distribution over the specimen surface, either of the contamination speed or of the amount of the specimen breakdown or of the sum of the two factors.

Accordingly, it will be seen, even upon neglecting the difiiculties in determining the working point for obtaining the contamination speed zero in connection with a specific specimen, that it is hardly possible to obtain with the known cooling device for all specimen regions the contamination speed zero with negligible specimen breakdown.

It may also be mentioned in connection with the explanations referring to the state of the art, that the injection of air or other gases into the region of the specimen has been found advantageous as a measure which noticeably reduces the contamination speed. However, this measure likewise entails difficulties in the technical realization of the method, since it depends upon the gas pressure and since the gas pressure may possibly cause destruction of the specimen.

Upon considering the above outlined state of the art, it will be seen that there is need for a device which reliably permits prevention of the specimen contamination as well as the specimen breakdown, for intervals of time which are long enough for unhurriedly efiecting investigations with a corpuscular ray apparatus, for example, production of electron microscopic pictures, wherein the influences concerning special operating conditions as well as action of the respective specimen do not enter.

The object of the invention is to provide such a device, proceeding from a corpuscular ray apparatus operating on the pump, especially an electron microscope, comprising a specimen cartridge for receiving the specimen car- "rier, such cartridge being connected with a deep freeze device. The construction for realizing this object comprises, in accordance with the invention, a specimen cartridge havingtwo mutually heat insulated parts, one of said parts holding the specimen carrier and being together therewith disposed in good heat conducting connection with parts of the corpuscular ray apparatus which are at least approximately at room temperature, while the second cartridge part forms a cooling chamber surrounding the specimen carrier in heat insulating relation with respect thereto, said cooling chamber having walls which conduct heat well and being in good heat conducting manner connected with the deep freeze device.

The construction according to the invention is in view of the above described state of the art, based upon the surprising recognition of the fact that the relationship between contamination speed, specimen break-down and temperature of the cooling chamber, as shown in FIG. 1, applies only in a case in which the temperature of the specimen corresponds at least approximately to the temperature of the cooling chamber, while a wide temperature region results in a case in which the cooling chamber is cooled to sufficiently low temperatures with the specimen at least approximately at room temperature, in which region the contamination speed as well as the specimen break-down practically disappear. This relationship is apparent from FIG. 3.

Referring now to FIG. 3, the relationship corresponds up to temperatures of about -'100 C. largely to that which is represented in FIG. 1. The specimen break-down is reduced below 100 C. (all temperature data may 'fiuctuate within a given more or less wide range), reaching just as the contamination speed, practically the value zero, at a cooling chamber temperature of about 130 C., and retainin'g'this value even upon-further cooling of d the cooling chamber, which is particularly important for practical work.

However, this work or operation diagram presupposes that the specimen is at least approximately at room temperature or possibly at a higher temperature. This circumstance may be explained physically by the fact that the partial pressure of the water vapor in the vacuum space of the corpuscular ray apparatus drops relatively steeply at a temperature in the vicinity of C. or somewhat less. An explanation with respect to the partial pressure of the hydrocarbon substances involved in the contamination is impossible since the partial pressure of such hydrocarbon substances has already strongly dropped at higher temperatures.

The fact that it is not the partial pressure of the hydrocarbon substances according to the above discussed paragraph (l) but the partial pressure of the water vapor which is in this connection of decisive importance, represents a revision of the current opinions concerning respectively the physical and chemical basis of the problem which is being treated here, insofar as the aspects noted in paragraph (4), having to do with the influences of other particles impacting the specimen surface, have been neglected until now. The recognition of the influence of the partial pressure of the water vapor as a cause for the specimen break-down also serves as an explanation for the fact that the specimen break-down disappears at identical temperatures within the cooling chamber only when the specimen is not correspondingly cooled, that is, when it is at least approximately at room temperature. It is to be considered in this connection that since the dwelling time of the water molecules upon the specimen-as before the dwelling time of the hydrocrabon molecules as arr explanation for the specimen contaminationis the shorter the higher the temperature of the specimen, the danger of the action of the water vapor molecules, that is, the danger of specimen break-down with increasing specimen temperature is reduced under the influence of the corpuscular ray upon the specimen surface.

Any specimen contamination or specimenbreak-down that may be observable below the upper limit temperature of the most favorable working range, indicated in FIG. 3 at about C., is believed to be traceable to the fact that the vicinity of the specimen is not completely covered with cooled surfaces owing to the required ray entry aperatures in the cooling chamber. This residual break-down or residual contamination may be held negligibly small by making as small as possible, the spatial angle under whichthe ray passage apertures appear as seen from the specimen.

According to the invention, the corpuscular ray apparatus may be so constructed that the two cartridge parts, one of which contains the specimen carrier and'is held at least approximately at'roorn'temperature whilethe other forms the cooling chamber surrounding the specimenicarrier, are provided with braces or struts which extend from one to the other part, so that the mounting for the specimen carrier at the first cartridge part lies with respectto the second cartridge partin heat insulated relation within the cooling chamber formed by the latter. The first cartridge part contains advantageously the cartridge cone serving for the'iusertion of the specimen cartridge in a table, care being taken that the cartridge cone is in good heat conducting connection with the table. Accordingly, the table constitutes in this embodiment of the invention, the part of the corpuscular ray apparatus which is at least approximately at room temperature and with which the first cartridge part is connected .in good heat conducting relation.

It will be necessary in given cases to provide in connection with the table, in view of the low heat capacity thereof, auxiliary means, for example, springs, webbing or the like, for improving the heat conduction'therebetween and the remaining parts of the corpuscular ray apparatus. Thea'dvantage of springs, webbing orthe like resides in that such elements do not aflfect a motion which may be imparted to the table.

In a preferred embodiment of the invention, the cooling chamber is formed by a potlike part which is held in heat insulating manner at the table and has a cover member provided with struts in starlike arrangement, such part being constructionally assigned to the first cartridge part for assembly therewith, the struts cooperating in the cover member with a strutlike arrangement of the adjacent region of the cartridge cone, extending laterally beyond such region, and lying with inserted specimen cartridge upon contact pieces which are in good heat conducting connection with the deep freeze device.

Bolts adapted for good heat conduction may serve for holding the potlike part at the table, such bolts extending through the table with the aid of heat insulating intermediate members and carrying contact pieces at their ends which face away from the potlike part, thus connecting the contact pieces in good heat conducting manner with the deep freeze device. These bolts may within the scope of the invention likewise be designated as struts between which extend parts of the table for good heat conducting connection with the cartridge cone.

The last described manner of holding the potlike part at the table, by means of good heat conducting bolts, makes it particularly possible to use a ring-shaped or annular contact piece as a backing for the struts of the cover member.

Another embodiment of the invention is thereby characterized that the two cartridge parts, due to mutual penetration in the lower region of the first cartridge part and in the upper region of the second cartridge part, are in the direction of the corpuscular ray disposed serially one in back of the other, in the manner of tWo chain links, and insertible in common. Thermal insulation problems arise in such arangement only along relatively small regions of the two cartridge parts.

The two serially arranged cartridge parts are advantageously mutually tensioned by means of springs. This is particularly important when the first cartridge part is insertible into the table and the second cartridge part into a heat insulating receiver member which is in good heat conducting connection with the deep freeze device, preferably at the objective lens, that is, for example, at the pole piece of the objective, since care must be taken in such embodiment of the invention to provide upon motion of the table for a relative motion between the first and second cartridge part. Accordingly, the struts in the two cartridge parts are to be dimensioned and arranged with a view of the greatest possible table motion.

A cone in the second cattridge part serves advtantage ously for the insertion of the second cartridge part into the heat insulating receiver member, such cone lying in continuation of the first cartridge cone serving for the insertion into the table and having a smaller diameter than the latter. Accordingly, there are as to outer appearance two cones lying serially in the direction of the corpuscular ray or beam, the second cone having a smaller diameter than the first. The two cones are mutually connected in chain link fashion by the previously described struts.

While it was in some cases found appropriate to construct the holding means for the specimen carrier as a spring holding means into which the specimen carrier is simply inserted, it is of advantage to construct the cooling chamber, that is, the second cartridge part, with a screw thread so as to facilitate exchange of the specimen carner.

As previously mentioned, the arrangement of the ray or beam entry apertures is of importance so far as the residual contamination and residual break-down are concerned. It is, therefore, proposed to form the ray entry apertures of the cooling chamber by cooled diaphragms, especially double diaphragms, so as to limit the spatial angle as seen from the specimen. The residual contamination and residual break-down, respectively, become 21- ready quite small when the ratio of diaphragm radius to the spacing of the diaphragm from the specimen amounts at the most to 1:8. Practically no disturbing specimen changes could be ascertained at a ratio of 1:20. It is understood, of course, that these values fluctuate depending upon the specimen and investigation conditions.

The deep freeze device which is in good heat conducting connection with the cooling chamber, may in known manner comprise a vessel for the cooling agent, which is filled with liquid air or the like, and a cooling rod which is advantageously resiliently pressed against the cooling chamber, such cooling rod establishing a good heat conducting connection between the cooling vessel and the cooling chamber.

The use of such a deep freeze device makes it possible to arrange the vessel for the cooling agent outside of the housing proper of the corpuscular ray apparatus, so that it is easily accessible.

A thermo element may be arranged at the cooling chamber, for effecting temperature measurements, with lines disposed in the cooling rod and carried outwardly.

It is particularly advantageous to arrange the vessel for the cooling agent or cooling medium in heat insulated manner in an extension which is flanged vacuumtight to the housing of the corpuscular ray apparatus, such extension being connected with the vacuum space of the apparatus. The cooling medium is thus practically likewise in the vacuum space of the apparatus. The arrangement provides the advantageous possibility of disposing at the eX- tension filling tubes for the cooling medium which tubes are sealed vacuumtight with respect to the vacuum space.

The various heat exchange or heat transition resistances are in accordance with the previously noted theoretical considerations so selected that the cooling chamber can be cooled at least to a temperature amounting to C.

In the specimen cartridge for an electron microscope, shown in FIG. 4, the first cartridge part which is at least approximately at room temperature and holds the specimen carrier 1, is formed substantially of the cartridge cone 2 which is inserted in the table 3 (details of which are of no interest here) and the holder 4 for the specimen carrier 1. It will be seen that the cartridge cone 2 is in good heat conducting contact with the holder 4 which is in turn in good heat conducting connection with the resiliently held specimen carrier 1, and otherwise in good heat conducting connection with the table 3 which is practically at room temperature.

The second cartridge part which is cooled by the cooling rod 5 which is part of the otherwise not illustrated deep freeze device, comprises substantially the potlike piece 6 which carries at the bottom end thereof the double diaphragm arrangement 7, and the cover 9 having struts 8 arranged in star formation, the cover 9 being held in the region of its tubular extension 16 by means of heat insulating intermediate members 11 and the spring 12 disposed in the bore of the cartridge cone 2. The cover 9 carries the upper aperture diaphragm 9a.

The potlike part 6 is held at the table 3 by means of bolts 14 which are with the aid of heat insulating intermediate members 13 extended through the table 3, only one such bolt 14 being visible in FIG. 4. The bolts 14 also serve to establish on the one hand a good heat conducting connection between the contact ring 15 which forms a backing for the struts 8 of the cover 9 and on the other hand over the potlike member 6 with the cooling rod 5.

In the embodiment shown in FIG. 4, the first cartridge part which is formed substantially by the cartridge cone 2 and the holder 4 for the specimen carrier, is connectible with the cover member 9 of the second cartridge part. A tool may be used for this purpose which cooperates with the struts 16 of the cartridge cone 2, these struts may be provided, for example, with an internal thread for a screwlike tool.

The tubular extension It; carries at the lower end there.- of, as seen in the drawing, the tubular parts 17, 18 which provide for cooling the vicinity of the specimen.

It will be seen that there are spaces formed in the specimen cartridge, between the parts which are at different temperatures, such spaces being dimensioned, just like the flow resistances obtained by corresponding configuration of the individual structural elements, so as to obtain within the cooling chamber a temperature below 130 C.

Below the specimen cartridge is disposed the pole piece system 1? for the objective, details of such system being here of no interest.

FIG. 5 shows a vertical section and FIG. 6 a transverse section through a second embodiment of the invention. In this embodiment, the two cartridge parts 2% and 21 are owing to mutual interconnection, in alignment with the direction of the corpuscular ray, of the lower portion of the cartridge part and the upper portion of the second cartridge part 21, serially successively disposed in the direction of the corpuscular ray, in the fashion of two chain links. The two cartridge parts are connectible and insertable in common.

In this embodiment, the first cartridge part 20, which is inserted into a table 22 (details of which are omitted), contains the cartridge cone 23 which carries the caplilce insert 24 and over the intermediate member 25, the holder 26 for the specimen carrier 27. As will be seen from FIG. 6, the intermediate member is formed with two webs 28 and 29 arranged in its upper portion, such webs merging in the lower portion in the nut 25a. Webs 30 and 31 in the cover member 32 of the second cartridge part 21 are disposed between the webs 28 and 2% and above the nut 25a, but do not contact the intermediate member 25. The second cartridge part 21 contains in addition to the cover member 32 also the parts 33 and 34 which are threadedly connected to form the potlike member. The part 34 carries a cooled double diaphragm arrangement 35. As shown in FIG. 5, the upper double diaphragm arrangement 36 is held by tubular extensions of the cover member 32. Numeral 37 indicates the cooling rod of the deep freeze device, details of which have been omitted.

The two cartridge parts 20 and 21 are resiliently mutually tensioned with the aid of a compression spring 38 which is held by means of heat insulating members 39 and 4-0 which are also adapted to act in electrically insulating manner.

The arrangement and size of the struts in the lower region of the first cartridge part 2t} and in the upper region of the second cartridge part 21, as well as the resilient connection of the two cartridge parts, provide for a possibility of moving the specimen disposed upon the specimen carrier 27, by imparting motion to the table 22, despite the fact that only the first cartridge part 20 is inserted in the table 22 while the second cartridge part 21 is disposed in the heat insulating receiver part 41 at the objective lens.

.FIG. 7 shows a suitable deep freeze device for the corpuscular ray apparatus according to the invention. The deep freeze vessel 76 is arranged heat insulated in the extension 72 which is flanged to the housing 71 of the apparatus. The extension is provided with a connecting member 74 which can be closed by means of a stopper 73, a tube 75 extending from the connecting member serving for the filling of the vessel 73 with the cooling agent. The stopper 73 is provided with a channel 76 formed therein for preventing excessive pressure.

The cooling rod 78 is in good heat conducting relation connected with the cooling vessel 70, over the band 77, the cooling rod being advantageously resiliently connected with the second cartridge part or the receiver member therefor, thus establishin a good heat conducting connection betweenthe respective part and the cooling rod and cooling agent, respectively.

Detailed explanations with respect to required sealing means and heat insulating inserts are omitted since the arrangement and construction thereof are apparent from the drawing and since there are many possibilities for variations.

As will be seen upon considering the vacant space 79 between the cooling rod 78 and the lead-through therefor which is substantially formed by the bushing 86, that there is a direct connection between the vacuum space of the corpuscular ray apparatus and the interior space of the extension 72.

The invention is not inherently limited to the described and illustrated embodiments. It is, for example, possible to provide wires in a small groove formed in the cooling rod 78 (FIG. 7) for outwardly conducting voltage appearing at a thermoelement disposed at a suitable point in the second cartridge part. Such a wire is indicated in FIG. 5 by numeral 81. It is so far as the principle is concerned likewise possible to use a deep freeze device differing from the one shown in FIG. 7. Moreover, measures may be taken for holding individual parts of the specimen cartridge at a defined potential. Special potential connections may in given cases be provided for this purpose since the individual structural elements are by heat insulating and therefore generally also electrically insulating members insulated mutually and with respect to grounded parts of the corpuscular ray apparatus. Double lenses may be avoided in given cases.

The use of the measures according the invention is likewise not inherently limited to electron microscopes. The invention may indeed be used generally in connection with corpuscular ray apparatus operating on the pump, wherein the danger of specimen contamination exists.

Changes may be made within the scope and spirit oi the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

I claim:

1. A corpuscular apparatus, operating in conjunction with an evacuating pump, especially an electron microscope, comprising an object cartridge having two can tridge parts disposed in heat insulated relation to one another, a specimen carrier, the first of said cartridge parts holding the specimen carrier and being with such carrier in good heat conduct'mg connection with parts of the corpuscular ray apparatus having at least approximately room temperature and capable of maintaining the specimen carrier at close to room temperature, the second cartridge part having walls of good heat conducting capacity and forming a chamber the walls of which are operatively connected in good heat conducting relation with a deep freeze device, the cooling chamber so formed surrounding the specimen carrier in heat insulated relation with respect thereto.

2. Corpuscular ray apparatus according to claim 1, wherein the cooling chamber can be cooled at least to a temperature of C.

3. Corpuscular ray apparatus according to claim 1, thereby characterized that the two cartridge parts are provided with struts which are mutually interlaced so that the mounting for the specimen carrier at the first cartridge part lies with respect to the second cartridge part in heat insulated relation within the cooling chamber formed by the second cartridge part.

4. Corpuscular ray apparatus according to wherein the first cartridge part contains the cartridge cone serving for the insertion of the specimen cartridge in a table, said cone being in good heat conducting relation with respect to the table.

5. Corpuscular ray apparatus according to claim 4, characterized by the provision, at the table, of auxiliary heat conducting means which improve the heat conduction between the table and the remaining parts of the corpuscular ray apparatus without afifecting motion to be imparted to the table.

a. Corpuscular ray apparatus according to claim 4, thereby characterized that the cooling chamber is formed claim 1,

by a potlike member which is disposed in heat insulated relation with respect to the table, and a cover having radially extending struts arranged thereon, said cover being structurally assembled with the first cartridge part and insertable therewith, said struts in the cover extend ing between a strutlike formation connecting the adjacent portion of the cartridge cone and the portion of the first cartridge part holding the specimen carrier, and upon insertion of the specimen cartridge upon contact means which is in good heat conducting relation with the deep freeze device.

7. Corpuscular ray apparatus according to claim 6, characterized by the provision of good heat conducting bolts which secure the potlike part to the table, heat insulating inserts cooperable with said bolts, such bolts extending through the table, insulated therefrom by said heat insulating inserts, and carrying the contact means at the ends thereof which face away from the potlike part, thereby connecting said parts over said pot-shaped part in good heat conducting relation with the deep freeze device.

8. Corpuscular ray apparatus according to claim 7, wherein said contact means has an annular configuration.

9. Corpuscular ray apparatus according to claim 4, wherein portions of the two cartridge parts are joined so as to dispose such cartridge parts serially in an interlocking relation, corresponding to that of chain links, in the direction of the corpuscular ray.

10. Corpuscular ray apparatus according to claim 9, comprising spring means for mutually tensioning said cartridge parts.

11. Corpuscular ray apparatus according to claim 10, wherein the first cartridge part is insertable at the table, and a heat insulating receiving member, disposed in good heat conducting connection with the deep freeze device, in which last mentioned member the second cartridge part is insertable.

12. Corpuscular ray apparatus according to claim 11, wherein the struts in the two cartridge parts are dimensioned and arranged to provide maximum spacing therebetween andfacilitate the greatest possible table motion.

13. Corpuscular ray apparatus according to claim 12, wherein the second cartridge part is provided with a cone for insertion into the heat insulating receiving member, which cone is longitudinally disposed relative to the cartridge cone serving for the insertion of the first cartridge part into the table, and is of smaller diameter than that of the cartridge cone.

14. Corpuscular ray apparatus according to claim 13,

wherein the second cartridge forming the cooling chamber is constructed in sections secured together by a screw thread to enable separation thereof and exchange of the specimen carrier.

15. Corpuscular ray apparatus according to claim 14, comprising cooled diaphragms forming the ray entry apertures of the cooling chamber for the limitation of the spatial angle as seen from the specimen.

16. Corpuscular ray apparatus according to claim 15, wherein the ratio of diaphragm radius to the spacing of the diaphragm from the specimen is at the most equal to 1:8.

17. Corpuscular ray apparatus according to claim 1, wherein the deep freeze device comprises a vessel filled with a cooling agent, and a cooling rod which is resiliently in engagement with the cooling chamber and provides a good heat conducting connection between the cooling vessel and the cooling chamber.

18. Corpuscular ray apparatus according to claim 17, comprising a voltage producing thermoelement for measuring the temperature at the cooling chamber, and conductor means disposed in the cooling rod for conducting voltage from said thermoelement exteriorly of the apparatus.

19. Corpuscular ray apparatus according to claim 17, wherein the vessel for the cooling agent is disposed in heat insulating relation in an extension secured in vacuumtight relation to the corpuscular ray apparatus which extension is in communication with the vacuum space thereof.

20. Corpuscular ray apparatus according to claim 19, wherein said extension comprises tube means for supplying cooling agent to said vessel, said tube means being sealed with respect to the vacuum space.

References Cited UNITED STATES PATENTS 2,826,701 3/1958 Columbe 25049.5 2,858,444 10/1958 Leisegang 25049.5 3,124,680 3/1964 Van Dorsten et al. 25049.5

FOREIGN PATENTS 921,218 12/1954 Germany. 927,282 5/1955 Germany.

WILLIAM F. LINDQUIST, Primary Examiner. RALPH G. NILSON, Examiner. 

1. A CORPUSCULAR APPARATUS, OPERATING IN CONJUNCTION WITH AN EVACUATING PUMP, ESPECIALLY AN ELECTRON MICROSCOPE, COMPRISING AN OBJECT CARTRIDGE HAVING TWO CARTRIDGE PARTS DISPOSED IN HEAT INSULATED RELATION TO ONE ANOTHER, A SPECIMEN CARRIER, THE FIRST OF SAID CARTRIDGE PARTS HOLDING THE SPECIMEN CARRIER AND BEING WITH SUCH CARRIER IN GOOD HEAT CONDUCTING CONNECTION WITH PARTS OF THE CORPUSCULAR RAY APPARATUS HAVING AT LEAST APPROXIMATELY ROOM TEMPERATURE AND CAPABLE OF MAINTAINING THE SPECIMEN CARRIER AT CLOSE TO ROOM TEMPERATURE, THE SECOND CARTRIDGE PART HAVING WALLS OF GOOD HEAT CONDUCTING CAPACITY AND FORMING A CHAMBER THE WALLS OF WHICH ARE OPERATIVELY CONNECTED IN GOOD HEAT CONDUCTION RELATION WITH A DEEP FREEZE DEVICE, THE COOLING CHAMBER SO FORMED SURROUNDING THE SPECIMEN CARRIER IN HEAT INSULATED RELATION WITH RESPECT THERETO. 